Extraction of cerium with an organic solvent



Patented Oct. 28, 1952 I i 2,615,798 CTION: -Q tiilMi-M M -0RGANIC SOLVENT I Edgarf- C. Pitzer, ("S chenecta'dy, 'i assig'nor to the Uiiited states 01: America asrrepresented -'by we ll liited LSta'tes Atomic :Ei lergy Commis- "wormin implicating-March$51951,

*Serial No. 214*,20'4

I 12 Claims. (01. 23312) -i 1 2 rhis invention :deals with -=the extraction of a*s'atisfactoryberiumextraction, =thedichromate cerium cations from aqueous solutions' withan concentration should be maintained at between organic solventand .in particular with the ex- '0. 0004' and -'.01xM but :preferably between-0.001

traction or cerium valuespreserit in "tracer c'onand 0.005 M; centra'tiOn QbyeanS of awater imniiscihleali- I'h'e extraction of the :cerium .values is furp'haticke'tone. thermore improved :by' :adding, .a r'saltingout It is an object of this invention to provide a agent to the aqueous solution. Water soluble process by which the extraction of cerium is consubstances which have an anion in common with siderably increased. the salt to be extracted, such as acids or salts,

It has been found that the presence of dichroare particularly suitable. In case that cerium mate in the aqueous cerium salt solution, and in is present in the form of cerous nitrate, for inparticular the concentration in which the distance, nitric acid, alkali nitrates including amchromate is present, critically influences the de- 'monium nitrate, alkaline earth metal nitrates, gree of solvent extraction of cerium values disaluminum nitrate, chromium nitrate and ferric solved in tracer concentration when substannitrate are suitable. The extraction is increased tially water-immiscible aliphatic ketones are with an increase of salting-out agent concenused as the solvent. tration.

Experiments showed that the function between Although the salting-out agents may be neu dichromate concentration and extractability is tral salts, it has been found that the extraction quite complex and by no means directly proporis still furthermore improved if it is carried out tional. It was found that a critical range of difrom a mineral acid aqueous solution; also in chromate concentration exists in which a maxithis case the efiiciency is higher with higher mum extraction is obtained. acid concentration;

This unexpected relationship between dicho- Hexone (methyl isobutyl ketone) is the premate concentration and extraction coeflicient ferred substantially water-immiscible aliphatic will be better obvious from the tests compiled in ketone. Also the ketone is preferably used in the table below. In all of these tests aqueous acid condition, and a mineral acid concentration solutions were used which had a concentration of from 0.1 to 1 N is preferred for this purpose.

of Ce+++ of '7- 10 counts/min./ml., further- It will be understood that by applying a nummore containing aluminum nitrate in a conber of extraction stages, the total yield, or sepacentration of 1.2 M and nitric acid in a concenration, may be considerably increased. 7 tration of 0.15 M, but having varying concen- The solvent may be reconditioned for re-use' trations of sodium dichromate. The extractions by back-extracting the cerium values with a were carried out in each instance at room temsuitable aq Solution, a means ow 0 pemture t methyl i utm ketgne (hexone) those skilled in the art. For instance, an aqueous, which was 05 M in nitflc acid alkali-containing solution for the purpose of neutralizing the acid in the solvent is satis- Table factory for the back-extraction of the cerium.

Another solution suitable for stripping is an aqueous solution containing a reducing agent NMOWHM) (organic/ 40 such as hydrogen peroxide or ferrous salts by aquews) which the tetravalent cerium is reduced to the N0 nonextractable trivalent cerium. Moreover, the

-4 teaching of this invention may be utilized for the back-extraction, namely, by using a dichromate solution of a concentration outside the critical range, for instance a dichromate solution of at least 0.05 M.

It will be understood that this invention is not to be limited to the details given herein but that it may be modified within the scope of the ap From the values obtained in the above tests, pended claims,

and still better from a curve plotted from these t is claimed values, it is obvious that the concentration of di- A process f the separation of cerium chromate is critical and that, in order to obtain 05 v m from an aqueous Solution containing nitric acid.

. 3 cerium nitrate in a tracer concentration, comprising incorporating an alkali metal dichromate to obtain a concentration of from 0.0004 to 0.01

M, contacting the resultant aqueous solution with a substantially water-immiscible aliphatic ketone, and separating an aqueous phase and a ketone extract phase containing cerium values.

2. A process for the separation of cerium values from an aqueous solution containing cerium nitrate in a tracer concentration, comprising adding a salting-out agent to said solution, incorporating an alkali metal dichromate to obtain a concentration of from 0.0004 to 0.0]. M, contacting the resultant aqueous solution with a substantially water-immiscible aliphatic ketone, and separating an aqueous phase and a ketone extract phase containing cerium values.

3. The proces of claim 2 wherein the aqueous solution is a mineral acid solution.

4. The process of claim 2 wherein the dichromate concentration ranges between 0.0005 to 0.005 M.

5. The process of claim 2 wherein the dichromate is sodium dichromate.

"6. The process of claim 2 wherein the saltingout agent is a mixture of aluminum nitrate and 7. The process of claim 2 wherein the ketone is hexone.

8. The process of claim 2 wherein the ketone is acidified hexone.

9. The process of claim 2 wherein the aqueous solution is a nitric acid solution and. the ketone is hexone containing nitric acid.

10. The process of claim 9 wherein the hexone contains nitric acid in a concentration of from 0.1 to l M.

11. The process of claim 2 wherein the aqueous solution contains 1.2 M aluminum nitrate and 0.15 M nitric acid and the ketone is hexone containing 0.5 M nitric acid.

12. The process of claim 11 wherein the dichromate concentration ranges from 0.001 to 0.005 M.

' EDGAR C. PITZER.

REFERENCES CITED The following references are of'record in file of this patent:

the 

1. A PROCESS FOR THE SEPARATION OF CERIUM VALUES FROM AN AQUEOUS SOLUTION CONTAINING CERIUM NITRATE IN A TRACER CONCENTRATION, COMPRISING INCORPORATING AN ALKALI METAL DICHROMATE TO OBTAIN A CONCENTRATION OF FROM 0.0004 TO 0.01 M, CONTACTING THE RESULTANT AQUEOUS SOLUTION WITH A SUBSTANTIALLY WATER-IMMISCIBLE ALIPHATIC KETONE, AND SEPARATING AN AQUEOUS PHASE AND A KETONE EXTRACT PHASE CONTAINING CERIUM VALUES. 